Beginning in the Middle Ages, when rawhide boots were tied onto horse's hooves, horse owners have sought to remedy the hoof problems of domesticated horses. Following these earliest attempts at protecting the horse's feet, metal horseshoes were developed that are nailed to the outer rim of the sole.
However, in spite of the long history of horseshoes and their importance in maintaining equine health there has been little in the way of research and investigation into the interaction between horseshoes and hoof physiology. It is only recently that well directed scientific investigations, including studies of a large number of wild horses have shown that many generally accepted traditional beliefs about horseshoes and hoof care are untrue and have in fact contributed to chronic hoof problems in domestic horses.
Among other things, studies have shown that horses having thin hoof walls, thin soles and contracted heels are minimal occurrences in wild horses. In general, barefoot wild horses have much better feet than domestic horses. Like domestic horses, angles of the hoof wall to the ground vary some but are generally around 55 degrees. The feet of wild horses that travel over abrasive surfaces are fairly short with a healthy horn mass that is rounded aggressively to the border of the sole. Less outer wall radius is seen in areas where the ground is more forgiving. In all instances the walls, soles and frogs are thick and dense. These features allow wild horses to travel barefoot over great distances on very hard terrain while still remaining sound.
To the contrary, domestic horses traditionally travel over less varied terrain and hence do not get the continual stimulation, irritation and abrasion that is necessary to keep the hoof wall worn and rounded to the same level as the sole, especially in the anterior portion of the hoof. The functional sole that is generated around the peripheral border and ventral surface of the coffin bone (PIII) regulates the hoof wall length. In the natural setting the sole becomes harder and more durable than the hoof wall itself because of its ability to adjust for changes in the environment, (i.e. wet or dry, soft or hard). In light of the adaptive ability of the sole and its function in regulating the length of the hoof wall, the sole of the equine foot plays an important role in hoof balance. The optimal function of the equine foot depends on absorbing energy upon ground contact and maintaining equilibrium while in motion to insure minimal stress and strain to the DIP joint.
These discoveries have increased the focus of farriers and veterinarians on means and methods of retaining the benefits of horseshoes while, at the same time, maintaining the innate natural hoof balance of wild horses and maintaining healthy distal phalanges alignment by reducing unnatural stress on the tendons and joints in the lower leg of the horse.
The U.S. patents to Duckett, U.S. Pat. Nos. 5,165,481 and 5,368,104 are examples of prior efforts to fix a balance point on a horseshoe that has a relationship with the axis of rotation of the coffin bone (PIII) about the second phalanx (PII), similar to the unshod hoof of a wild horse.
Antecedent to the improved method of the present invention is the acknowledgement that a horse's feet are not all alike, much the same as humans. The likeness of the two front feet for example, is remote. A pair of feet will differ in dorsal hoof angle, width and size. Feet will also differ in the distance measured in the sagital plane between a lateral line connecting the widest parts of the sole and a vertical line passing through the distal interphalangeal joint (DIP joint or coffin joint). Conventional farriery teaches that matching foot pairs is part of the goal in shoeing a horse. If there is a gross difference in foot pairs, a close compromise should be the approach, ignoring the basic truth that the feet are inherently different and should be treated individually. In fact, the entire assessment of foot balance is approached by external appearance of the hoof capsule and its relationship to the upper bones of the pastern.
In addition to the problems induced by this unscientific approach to applying a horseshoe, the prior practice of trimming a horse's hoof to raise the hoof angle also deserves correction. For instance, trimming less of the heel portion of the hoof wall to make the caudal portion taller allows the heel to grow forward and results in shortened distance from the widest part of the sole to the end of the heel. This trimming method results in minimized caudal support by moving the ground contacting portion of the heel buttress forward of the frog buttress. In addition, when the anterior part of the foot is longer than normal (or optimal), the force moment on the toe causes the anterior hoof wall to bend and extend forward, producing an unnatural and exaggerated reduction in the angle of the dorsal hoof wall to the ground. Such deformation of the hoof wall results in grossly unequal distances between the center of balance of the traditionally applied horseshoe at the toe and the center of balance with respect to the heel of the shoe. With this unequal positioning of the horseshoe, the whole foot is out of balance, leading to, among other things, overgrown heels that are weak and become crushed and painful because of their more forward location.
In addition to the problems associated with conventional heel trimming theory, the prior practice teaches that shoes should be fitted from front to back, a technique that accommodates and exacerbates an already distorted hoof, rather than resolving the distortion and normalizing the foot.